Letters Shed Light on 2008 Concerns about Libor Manipulation

Newly-revealed correspondence shows major interests on both sides of the Atlantic were at cross purposes.

When traders complained to the CME Group about the pricing of Libor at the height of the financial crisis in 2008, the world's largest futures exchange worried about the benchmark's credibility and urged changes that would have effectively made it harder to accuse bankers of rate fixing.

But the British Bankers' Association or BBA, which oversees the highly-influential interest rate, seemed comfortable that bankers were submitting...